Time is running out for Christmas shoppers, even more so for those who need to ship presents. This is the busiest week of the year for companies like FedEx and UPS.

We sent Rick Howlett of member station WFPL to UPS's air hub in Louisville, Kentucky.

RICK HOWLETT, BYLINE: UPS cargo jets are a familiar site in the Louisville sky, but arrivals and departures are a lot more frequent this week at the Worldport air hub.

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HOWLETT: Mike Hawkins oversees operations in one of the massive sorting wings, a dizzying maze of conveyor belts and red scanning lights. These packages will spend no more than four hours on the ground.

MIKE HAWKINS: When we get a container in and we unload a package, it won't get touched again until it gets down to an outbound spot. And it'll get sorted probably, you know, it gets scanned six or eight times.

HOWLETT: These packages are handled by an army of thousands of part-time workers. Jason Kaiser has worked for UPS for 15 years.

JASON KAISER: We know it's coming, you know, that's what we talk about all year is peak season. You just got to push through.

HOWLETT: More packages are being pushed through UPS facilities this holiday season. About 120 million, this week alone. Spokesman Mike Mangeot says volume is up about 6 percent from last year, due in large part to a boost in online sales.

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MIKE MANGEOT: Our peak season used to really be heavy for about a month between Thanksgiving and Christmas. We are seeing that get compressed more and more to about the last two weeks before Christmas.

HOWLETT: Mangeot says UPS hired about 55,000 seasonal workers around the world to help handle the holiday volume, including 800 in Louisville.

MANGEOT: Some of those folks will have the opportunity to stay on after the holidays, if they've done a good job and we have the need for the extra workers. A number of our high-level management employees actually got their start with the company in just that capacity.

HOWLETT: It's also been a happy holiday season for UPS rival FedEx. The Memphis-based company says its peak day shipments were up more than 10 percent from last year.